1. Field of the Invention
The present invention generally relates to an information record medium, and more particularly to an information record medium on which information can be optically recorded and reproduced in accompaniment with a tracking servo control of a so-called push-pull method.
2. Description of the Related Art
There is a DVD as an information record medium, whose record capacity is improved to be as high as several times of that of a conventional CD (Compact Disc), and on which video information and audio information in an information amount of one full move or the like can be recorded.
Other than the DVD dedicated for reproduction such as a DVD-ROM (DVD-Read Only), there is a so-called DVD-RW (DVD Re-recordable) as a DVD standard, on which the information can be reproduced and recorded at a plurality of times, and on which the information can be reproduced by an information reproducing apparatus for reproducing the DVD dedicated for reproduction.
Here, on an information record medium based on the DVD-RW standard, there is formed a groove track, which has a width of about 0.3 μm and a depth of about 20 nm (nanometer) and which is wobbled at a constant frequency, as an information track on which the optical information recording and reproduction is performed. At this time, the reason why the groove track is wobbled is to generate a record standard clock signal having an accurate frequency synchronous with the rotation of the DVD-RW, by detecting the frequency of the wobbling at the time of information recording.
On the other hand, the DVD-RW basically has a record capacity substantially same as that of the DVD dedicated for reproduction. Thus, the video information etc., recorded on the DVD dedicated for reproduction may be illegally copied onto the DVD-RW. At this time, the video information or the like recorded on the DVD dedicated for reproduction is generally protected by a copy right, so that the copy right holder drastically suffers losses if the above mentioned illegal copy is often performed.
Therefore, there is a countermeasure against such an illegal copy according to the DVD-RW standard that the area on the DVD-RW, which corresponds to the area where control information for controlling the reproduction is recorded on the DVD dedicated for reproduction, is set as an area where recording is impossible on the DVD-RW, to thereby prevent the illegal copy.
In addition to this, according to the DVD-RW standard, it is permitted to prepare an area dedicated for reproduction on the above mentioned area where recording is impossible, and to record the predetermined reproduction control information etc., in advance in this area. Further, according to the DVD-RW standard, the phase pit, which is used in the DVD dedicated for reproduction, is also used to record this predetermined reproduction control information etc., in the area dedicated for reproduction of the DVD-RW.
On the other hand, according to the DVD-RW standard, at the time of optically recording and/or reproducing the information by use of the light beam such as a laser light with respect to the DVD-RW, the tracking servo control is performed by means of the so-called push-pull method.
However, if it is attempted to obtain the tracking error signal by the push-pull method at the time of reproducing the reproduction control information, which is recorded in the area dedicated for reproduction by forming the phase pit, it may be difficult to obtain the tracking error signal and a detection signal corresponding to the reproduction control information at an adequate signal quality, because of an influence of an interference with a pre-pit formed in the area dedicated for reproduction in advance (i.e., a pre-pit, which is formed within a land track formed adjacent to the groove track and is to record address information (i.e., address information indicating a record position on the DVD-RW) which is used when recording the information onto the groove track other than the area dedicated for reproduction), which is a problem.